Simulations of Galactic polarized synchrotron emission for Epoch of Reionization observations

Spinelli, M.; Bernardi, G.; Santos, Mário G.

doi:10.1093/mnras/sty1457

Cited by 24 publications

(18 citation statements)

References 56 publications

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“…We simulated realistic observations taken with a zenith-pointing dipole, spanning an 8 hour range with a 1 minute cadence. Simulations include the allsky polarized foreground template maps from Spinelli et al (2018) and a realistic dipole beam in order to generate polarized spectra. We also include a different polarized template where the contamination is reduced to low Faraday depth values, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…We simulate two antenna orientations (x x and yy) separately, using the corresponding beam models. We also consider a more optimistic case where the amplitude is 10% of the template maps in order to empirically account for depolarization effects not included in the Spinelli et al (2018) model. Total intensity foregrounds are directly modelled through their spectra, as a 4 th -order log-polynomial function.…”

Section: Discussionmentioning

confidence: 99%

“…We use the simulations in Spinelli et al (2018, hereafter S18) to produce Stokes Q and U full sky maps in the 50-200 MHz range with 1 MHz frequency resolution. The S18 full sky simulations are based on the interferometric observations that sample up to degree angular scales (Bernardi et al 2013) that were extrapolated up to tens of degrees scales, relevant for global signal observations.…”

Section: Polarized Foreground Modelmentioning

confidence: 99%

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On the contamination of the global 21 cm signal from polarized foregrounds

Spinelli

Bernardi

Santos

2019

Monthly Notices of the Royal Astronomical Society

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Global (i.e. sky-averaged) 21 cm signal experiments can measure the evolution of the universe from the Cosmic Dawn to the Epoch of Reionization. These measurements are challenged by the presence of bright foreground emission that can be separated from the cosmological signal if its spectrum is smooth. This assumption fails in the case of single polarization antennas as they measure linearly polarized foreground emission -which is inevitably Faraday rotated through the interstellar medium. We investigate the impact of Galactic polarized foregrounds on the extraction of the global 21 cm signal through realistic sky and dipole simulations both in a low frequency band from 50 to 100 MHz, where a 21 cm absorption profile is expected, and in a higher frequency band (100 − 200 MHz). We find that the presence of a polarized contaminant with complex frequency structure can bias the amplitude and the shape of the reconstructed signal parameters in both bands. We investigate if polarized foregrounds can explain the unexpected 21 cm Cosmic Dawn signal recently reported by the EDGES collaboration. We find that unaccounted polarized foreground contamination can produce an enhanced and distorted 21 cm absorption trough similar to the anomalous profile reported by Bowman et al. (2018), and whose amplitude is in mild tension with the assumed input Gaussian profile (at ∼ 1.5σ level). Moreover, we note that, under the hypothesis of contamination from polarized foreground, the amplitude of the reconstructed EDGES signal can be overestimated by around 30%, mitigating the requirement for an explanation based on exotic physics.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Polarized Foreground Modelmentioning

confidence: 99%

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On the contamination of the global 21 cm signal from polarized foregrounds

Spinelli

Bernardi

Santos

2019

Monthly Notices of the Royal Astronomical Society

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“…In fact, the galactic synchrotron emission is highly polarized, and some point sources are also polarized [70]. The polarized emission is also very important in the foreground subtraction analysis, because the Faraday rotation induce an oscillation along the frequency which is similar to the 21cm signal [71][72][73][74][75][76]. Despite these limitations, the inclusion of the point source in this model increased the usable range of angular resolution, making it a useful tool for the study of foreground subtraction in 21cm experiment.…”

Section: Resultsmentioning

confidence: 99%

A high-resolution self-consistent whole sky foreground model

Huang

Chen

2019

Sci. China Phys. Mech. Astron.

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The neutral hydrogen 21cm line is potentially a very powerful probe of the observable universe, and a number of on-going experiments are trying to detect it at cosmological distances. However, the presence of strong foreground radiations such as the galactic synchrotron radiation, galactic free-free emission and extragalactic radio sources make it a very challenging task. For the design of 21cm experiments and analysis of their data, simulation is an essential tool, and good sky foreground model is needed. With existing data the whole sky maps are available only in low angular resolutions or for limited patches of sky, which is inadequate in the simulation of these new 21cm experiments. In this paper, we present the method of constructing a high resolution self-consistent sky model at low frequencies, which incorporates both diffuse foreground and point sources. Our diffuse map is constructed by generating physical foreground components including the galactic synchrotron emission and galactic freefree emission. The point source sample is generated using the actual data from the NRAO VLA Sky Survey (NVSS) and the Sydney University Molonglo Sky Survey (SUMSS) where they are available and complete in flux limit, and mock point sources according to statistical distributions. The entire model is made self-consistent by removing the integrated flux of the point sources from the diffuse map so that this part of radiation is not double counted. We show that with the point sources added, a significant angular power is introduced in the mock sky map, which may be important for foreground subtraction simulations. Our sky maps and point source catalogues are available to download. neutral hydrogen, 21cm line, foreground model, whole sky map, simulation PACS number(s): 95.80.+p, 95.85.Bh, 98.70.Dk, 95.75.Mn, 95.75.Pq Citation: Huang Q Z, Wu F Q & Chen X L, A high-resolution self-consistent whole sky foreground model, Sci. China-Phys. Mech. Astron. ??, 000000 (2018), doi: ? 1) https://lambda.gsfc.nasa.gov/product/foreground/haslam_408.cfm 2)

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“…Since the polarized emission from the Milky Way can have a very complex frequency dependence, a leakage of this signal to the total intensity can contaminate the cosmological 21-cm signal, making extraction and analysis more demanding ( [68,91,143] and see Fig. 6.15).…”

Section: Polarization Leakagementioning

confidence: 99%

Foregrounds and Their Mitigation

Chapman¹,

Jelić²

2019

The Cosmic 21-Cm Revolution

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The low-frequency radio sky is dominated by the diffuse synchrotron emission of our Galaxy and extragalactic radio sources related to Active Galactic Nuclei and star-forming galaxies. This foreground emission is much brighter than the cosmological 21 cm emission from the Cosmic Dawn and Epoch of Reionization. Studying the physical properties of the foregrounds is therefore of fundamental importance for their mitigation in the cosmological 21 cm experiments. This chapter gives a comprehensive overview of the foregrounds and our current state-of-the-art knowledge about their mitigation.

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Simulations of Galactic polarized synchrotron emission for Epoch of Reionization observations

Cited by 24 publications

References 56 publications

On the contamination of the global 21 cm signal from polarized foregrounds

On the contamination of the global 21 cm signal from polarized foregrounds

A high-resolution self-consistent whole sky foreground model

Foregrounds and Their Mitigation

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